An involuntary and progressive loss in body weight is a common symptom of HIV infection (hereinafter "HIV-related cachexia"). Such weight loss can be conveniently categorized as "chronic" when the weight loss occurs gradually over a period of about three months, and "acute" when the weight loss occurs rapidly (i.e., over a period of less than about three months) with an eventual recovery of the lost weight. As defined by the Centers for Disease Control (hereinafter "CDC"), when such weight loss amounts to greater than a ten percent (10%) loss in baseline body weight and is combined with either chronic diarrhea (i.e., at least two loose stools per day for more than thirty days) or chronic weakness and fever (i.e., weakness and/or fever which has been constant or intermittent for more than thirty days) in the absence of a secondary infection (i.e., lack of an infectious agent other than HIV which may account for any of the referenced symptoms), the weight loss is classified as HIV-related wasting syndrome (hereinafter "wasting syndrome"). It is noted that, based upon this definition of the wasting syndrome, all persons afflicted with the wasting syndrome suffer from HIV-related cachexia, but only a portion of those suffering from HIV-related cachexia are afflicted with the wasting syndrome.
In contrast to starvation-induced weight loss, HIV-related cachexia results in profound tissue depletion that does not respond readily to nutritional therapy.
It has been suggested by various researchers in the field that the wasting syndrome would best be characterized by the degree of involuntary depletion of lean body mass, predominately muscle protein, rather than simply body weight. However, this suggestion has not been widely accepted by the medical community and is still being debated.
The wasting syndrome is known to play a major role in the decreased quality of life of AIDS patients, and constitute a major cause of morbidity and mortality in patients infected with HIV. After years of ignoring the syndrome, the CDC officially recognized the wasting syndrome as an AIDS-defining illness in 1987. Despite the use of antiretroviral agents, improvements in therapy and prophylaxis against many of the major disease complications, the prevalence of the wasting syndrome is increasing.
Etiology
It is widely believed that HIV-related cachexia and the wasting syndrome are mediated by a combination of factors including hypermetabolism, metabolic derangement, decreased caloric intake, malabsorption, cytokine activity, endocrine dysfunction, and myopathy.
Various treatment regimens have been investigated, including enteral & parenteral alimentation, appetite stimulants, anabolic agents, cytokine modulators and fatty acid supplements, with limited success. Hence, the search continues for alternative treatments for HIV-related cachexia and the wasting syndrome.